Quarterly report pursuant to Section 13 or 15(d)

Commodity Derivative Positions (Detail)

v3.8.0.1
Commodity Derivative Positions (Detail)
$ in Thousands
9 Months Ended
Sep. 30, 2017
USD ($)
bbl
$ / bbl
Dec. 31, 2016
USD ($)
Derivative Instruments Related to Oil and Gas Production [Line Items]    
Derivative Liability $ 18,557 $ 27,369
Settlement Agreement [Member]    
Derivative Instruments Related to Oil and Gas Production [Line Items]    
Fair Value Asset  
Fair Value Liability $ 172  
Crude Oil | Fourth Quarter 2017 [Member]    
Derivative Instruments Related to Oil and Gas Production [Line Items]    
Instrument Swaps  
Notional Volume, per day | bbl 4,381  
Derivative, Swap Type, Average Fixed Price | $ / bbl 48.59  
Fair Value Asset $ 0  
Fair Value Liability $ 1,361  
Crude Oil | First Quarter 2018 [Member]    
Derivative Instruments Related to Oil and Gas Production [Line Items]    
Instrument Swaps/Put option 1  
Notional Volume, per day | bbl 8,513  
Derivative, Swap Type, Average Fixed Price | $ / bbl 47.98  
Fair Value Asset $ 0  
Fair Value Liability $ 2,427  
Crude Oil | Second Quarter 2018 [Member]    
Derivative Instruments Related to Oil and Gas Production [Line Items]    
Instrument Swaps/Put option 1  
Notional Volume, per day | bbl 8,484  
Derivative, Swap Type, Average Fixed Price | $ / bbl 47.98  
Fair Value Asset $ 0  
Fair Value Liability $ 1,971  
Crude Oil | Third Quarter 2018 [Member]    
Derivative Instruments Related to Oil and Gas Production [Line Items]    
Instrument Swaps/Put option 1  
Notional Volume, per day | bbl 8,455  
Derivative, Swap Type, Average Fixed Price | $ / bbl 47.98  
Fair Value Asset $ 0  
Fair Value Liability $ 1,563  
Crude Oil | Fourth Quarter 2018 [Member]    
Derivative Instruments Related to Oil and Gas Production [Line Items]    
Instrument Swaps/Put option 1  
Notional Volume, per day | bbl 8,455  
Derivative, Swap Type, Average Fixed Price | $ / bbl 47.98  
Fair Value Asset $ 0  
Fair Value Liability $ 1,251  
Crude Oil | First Quarter 2019 [Member]    
Derivative Instruments Related to Oil and Gas Production [Line Items]    
Instrument Swaps  
Notional Volume, per day | bbl 2,946  
Derivative, Swap Type, Average Fixed Price | $ / bbl 49.87  
Fair Value Asset $ 0  
Fair Value Liability $ 356  
Crude Oil | Second Quarter 2019 [Member]    
Derivative Instruments Related to Oil and Gas Production [Line Items]    
Instrument Swaps  
Notional Volume, per day | bbl 2,921  
Derivative, Swap Type, Average Fixed Price | $ / bbl 49.87  
Fair Value Asset $ 0  
Fair Value Liability $ 307  
Crude Oil | Third Quarter 2019 [Member]    
Derivative Instruments Related to Oil and Gas Production [Line Items]    
Instrument Swaps  
Notional Volume, per day | bbl 2,897  
Derivative, Swap Type, Average Fixed Price | $ / bbl 49.87  
Fair Value Asset $ 0  
Fair Value Liability $ 258  
Crude Oil | Fourth Quarter 2019 [Member]    
Derivative Instruments Related to Oil and Gas Production [Line Items]    
Instrument Swaps  
Notional Volume, per day | bbl 2,898  
Derivative, Swap Type, Average Fixed Price | $ / bbl 49.87  
Fair Value Asset $ 0  
Fair Value Liability $ 231